The Catholic teaching, as it applies here, is that we are bound by the Sacraments,but God is not.
God can bestow his grace on anyone he desires.
We, however, cannot rely on this hope and assume, therefore, that the normative means of our reception of sanctifying grace isn’t necessary.
Ah, now we are getting out of the woods

.
This situation, however, places us between a rock and a hard place. Does it not?
For example, why would anyone want to delay baptism? If we indeed took this as seriously as the teaching stresses. It would be prudent of us and the Church to arrange baptism immediately after birth, as circumstances allow. Why would anyone, in their right mind, want to delay a means of sanctifying grace?
Take RCIA for example. Baptism is delayed, on purpose, to ensure that the catechumen has full knowledge of what the Catholic Church is and at a minimum, Her basic teaching of the Faith. I can see where the teaching of Baptism of desire can have its origins in. In this case, were the catechuman to die before he is received into the Church - we would have withheld a means of sanctifying grace to this soul.
On the other hand, we have no problem accepting Triune baptismal formula from other Christian faiths.
If we were to take seriously the fact, like you have correctly expressed, that “we cannot rely on this hope and assume” that God will give His grace to this catechumen — it would be prudent for us to baptize this soul and then continue on with his education and carry on the normal calendar schedule for the rest of the sacraments.
After all, the eunuch didn’t have to enroll in classes before baptism

. In fact, baptism is the one thing throughout Scriptures that is given immediately upon reception into the Church.
I completely understand the need of education for confirmation and more importantly - first communion.
I will always have a hard time understanding that one of this little fellas:
http://i3advantage.com/blog/wp-content/uploads/2014/04/smiling-baby.jpg
Is deserving of eternal damnation. As it has been expressed here.